# include <stdio.h>
int main ()
{
  double a,b,c;
    printf("请输入变量a，b，c\n");
	scanf("%lf",&a);
	scanf("%lf",&b);
	scanf("%lf",&c);

	if(a+b>c&&a+c>b&&b+c>a)
	{ 
		printf("C=%lf\n",a+b+c);
	}

	else
	printf("not a triangle\n");

	return 0;

}

